内存管理之memblock管理之移除块

此函数是整个memblock中分配和释放内存的核心函数，主要是对region操作。详细实现如下：

static int __init_memblock memblock_remove_range(struct memblock_type *type,
					  phys_addr_t base, phys_addr_t size)
{
	int start_rgn, end_rgn;
	int i, ret;

//先确定移除的逻辑块所在的region，这步就是隔离isolate操作。
	ret = memblock_isolate_range(type, base, size, &start_rgn, &end_rgn);
	if (ret)
		return ret;

//把整个region从指定类型中移除。
	for (i = end_rgn - 1; i >= start_rgn; i--)
		memblock_remove_region(type, i);
	return 0;
}
 
 
/**
 * memblock_isolate_range - isolate given range into disjoint memblocks

把给出的范围内的逻辑块从以所在的块中脱离出来，这样会增加一个新的region。

* @type: memblock type to isolate range for
 * @base: base of range to isolate
 * @size: size of range to isolate
 * @start_rgn: out parameter for the start of isolated region
 * @end_rgn: out parameter for the end of isolated region
 *
 * Walk @type and ensure that regions don't cross the boundaries defined by
 * [@base,@base+@size).  Crossing regions are split at the boundaries,
 * which may create at most two more regions.  The index of the first
 * region inside the range is returned in *@start_rgn and end in *@end_rgn.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
 
region[min, max]
 
pre -->  memory：  min<--------------|----------------|-------------------->max

示例：

0x1000----------0x5000-----------0x8000---------------0xc0000
 
base:0x5000, size:0x3000,
 
 
 
region1[min, 0x5000]        region2[0x8000, max]
 
now -->  memory： min<----------->        hole     <------------------->max
 
0x1000--------0x5000             0x8000-------------0xc0000

static int memblock_isolate_range(struct memblock_type *type,
					phys_addr_t base, phys_addr_t size,
					int *start_rgn, int *end_rgn)
{
	phys_addr_t end = base + memblock_cap_size(base, &size);
	int idx;
	struct memblock_region *rgn;

	*start_rgn = *end_rgn = 0;

	if (!size)
		return 0;

	/* we'll create at most two more regions 太多region，目前最大支持128个*/
	while (type->cnt + 2 > type->max)
		if (memblock_double_array(type, base, size) < 0)
			return -ENOMEM;
//依次对每个region确定大小和覆盖范围。

for_each_memblock_type(type, rgn) {
		phys_addr_t rbase = rgn->base;
		phys_addr_t rend = rbase + rgn->size;


		if (rbase >= end)
			break;
		if (rend <= base)
			continue;


		if (rbase < base) {
			/*
			 * @rgn intersects from below.  Split and continue
			 * to process the next region - the new top half.
			 */
			rgn->base = base;
			rgn->size -= base - rbase;
			type->total_size -= base - rbase;
插入新的region

memblock_insert_region(type, idx, rbase, base - rbase,
					       memblock_get_region_node(rgn),
					       rgn->flags);
		} else if (rend > end) {
			/*
			 * @rgn intersects from above.  Split and redo the
			 * current region - the new bottom half.
			 */
			rgn->base = end;
			rgn->size -= end - rbase;
			type->total_size -= end - rbase;

另外一种插入方式

memblock_insert_region(type, idx--, rbase, end - rbase,
					       memblock_get_region_node(rgn),
					       rgn->flags);
		} else {
			/* @rgn is fully contained, record it */
			if (!*end_rgn)
				*start_rgn = idx;
			*end_rgn = idx + 1;
		}
	}


	return 0;
}

static void memblock_remove_region(struct memblock_type *type, unsigned long r)
{
	type->total_size -= type->regions[r].size;
	更新大小

memmove(&type->regions[r], &type->regions[r + 1],
		(type->cnt - (r + 1)) * sizeof(type->regions[r]));
	type->cnt--;

更新总的region大小

	/* Special case for empty arrays */
	if (type->cnt == 0) {
		WARN_ON(type->total_size != 0);
		type->cnt = 1;
		type->regions[0].base = 0;
		type->regions[0].size = 0;
		type->regions[0].flags = 0;
		memblock_set_region_node(&type->regions[0], MAX_NUMNODES);
	}
}